June Can Jam: Slow Cooker Blueberry Butter

Well kids. The Tigress Can Jam challenge this month was anything that ended in “erries” and since this is my summer of fruit butters, I have made a batch of blueberry butter. Last weekend, my friend Shay and I took a little drive out to my favorite blueberry pickin’ spot in South Jersey and spent a couple of hours rattling berries from branches, filling our buckets and bellies.

However, the true treat of the day came when we rounded the corner of the farm stand in order to pay for our hauls. Standing right in front was my cousin Amy, out for a day of picking with her partner and two of their grandkids. We had one of those truly lovely moments, when you gape open-mouthed for a moment before laughing and falling into hugs.

Once home with my seven and a half pounds of berries, I spent several days eating them popcorn-style out of bowls, before hunkering down and making a preservation plan for the rest. Last year I called blueberry my foundational jam and that’s still a phrase that feels correct. I will always love that simple jam (in fact, I still have some from last year), but this time around I wanted to try something slightly different.

Originally I had planned to make a blueberry butter spiked with a hint of lavender, but this week was busy enough that I didn’t have a chance to get to Reading Terminal Market and that’s the only place close by where I can get food-grade lavender. So I went simple and stuck with my mom’s preferred flavor profile of lemon zest, cinnamon and just a bit of nutmeg.

Lately, I’ve been turning to two gadgets to make my preserving work just a little bit easier to accomplish. The first is my trusty Vita-mix. I grew up with the vintage chrome version of this incredible blender and so during wedding time last year, made it a priority to dedicate some of our gifted resources to acquiring my own.

While I had an inkling that it had the potential to be a transformative piece of equipment, I had no idea how it would revolutionize my jam making. Here’s what makes it so special: When you run it on very low speed, it doesn’t puree the fruit. It just chops it up into small bits, which coincidentally, are the absolutely perfect size for jams and butters. I know it’s a little bit unfair to rave about something that’s so darned expensive, but really, this thing has changed my life for the better.

The other small electrical appliance (that happens to be on the very other end of the cost spectrum) that I’m using all the time these days is my ancient, $3-at-a-thrift-store slow cooker. I’ve found that older slow cookers are far superior to newer ones, because they cook at lower temperatures. Truly, food safety regulations have made it so that what was once the high setting on the old pots is now the low setting on the new ones (you should never be able to achieve a boil in one of the pots from the seventies or eighties). And when you’re cooking a butter, you want to cook it as low and slow as you can. Slow cookers are truly perfect for this.

This particular butter reminds me a bit of blueberry pie, which makes it a winner in my book. Tomorrow morning, I’m having some friends over to do a little fruit butter tasting (in recent days, I’ve also made apricot butter and sweet cherry butter). We’ll see if they like the blueberry version as much as I do.

Put the pureed blueberries in a slow cooker. Place a lid on the pot and turn it on to low. After about an hour, give it a stir. At this point, you want to use something to prop the lid a bit. I found that laying a wooden spoon across the rim of the cooker and then placing the lid on gave it just enough room to let the steam evaporate.

My blueberry butter spent about six hours in the slow cooker (from 5:30 p.m. when I got home from work, until 11:30 p.m. when I canned and processed it). At the beginning of hour five, I added the spices and the sugar, removed the lid completely and turned the heat up to high, in order to speed the cooking down.

Once it’s cooked down sufficiently*, pour into jars (leave a good 1/2 inch of head space), wipe rims, apply lids and screw on bands. Process in a boiling water canner for 10 minutes. Eat on fresh scones and store unopened jars in a cool, dark place.

Notes

*When the cooking process is done, you can puree with an immersion blender or (carefully) in a regular blender, for a smoother product. It depends on whether you like your butters a bit chunky or very smooth.

148 Responses to June Can Jam: Slow Cooker Blueberry Butter

[…] do some jam, some preserves, some fruit leather, but first up was butter. I used Marisa‘s recipe again just using 8 cups of pureed apricots instead of blueberries. The smell in the crockpot was […]

Thanks for all of your inspirational posts! I just started canning this year and I tried your recipe for slow cooker blueberry butter. I had to halve the recipe and I think I may have added extra lime zest because the lime is pronounced in mine. Still I liked it a lot. While waiting for the results from the slow cooker, I made strawberry ice cream.

I have to thank you for this recipe, it is now one of my favorite treats in the morning. I changed it a little by using Splenda 1/2 instead of sugar the results worked out good. lucky we keep that old crock pot we got as a wedding gift, I can see a future for it again. I heard about your site off of Gardenfork Radio and since I had canned most my young life, but just got back into it, I thought I would check out your site for some tips and inspiration, and I am sure glad I did. Thank You for your hard work and I hope I can return the favor one day.
Joey

Done! Using the slow cooker was a great idea, considering we have had some too hot to turn the stove on type days. My 8 cups whole blueberries (then pureed down to something less…) made 4 cups lemony blue-butter, and yes, its delish!
The wine jelly i had in mind to get to this weekend may have to wait, since the August CanJam tomatoe butter sounds more intriguing than ketchup.
Thanks for the brilliant idea of putting the slow cooker to another good use.
I make a beautiful deep port coloured Italian Prune Plum butter with Chinese 5 Spice and this has been on almost every meat, bread and dairy product we have eaten this past year! Give that a try when your local plums are ready.

[…] Slow Cooker Blueberry Butter | Food in Jars I like to do a lot of small jars of different jams, condiments, etc. for holiday gifts. Last year I made apple butter, but I think would be a nice change and now is the time to make use of the billions of blueberries at the farmer’s market. (tags: gifts canning recipes) […]

Would this work with sour cherries? I expect I may have to adjust the sugar to make sure it’s sweet enough, but are there other adjustments you’d suggest? Thank you so much for blogging about preserving!

Hello,
I am making the blueberry butter right now. I find that it doesn’t look really blue or purple. It tastes good it looks more like chocolate. I have stirred it quite frequently so it doesn’t burn. And it has taken about 8 hours on low and still needs a bit more time. Let me know if I am doing this right.
Thanks for all the advice!
Kelly

[…] been picked up piecemeal from various farmers’ markets and produce shops. I made a batch of slow cooker blueberry butter with some of the Beechwood blues and ate the rest. That second flat has gone into smoothies, baked […]

a little cardamon does well too! I’m thinking this year’s batch with a spice trio cinnamon, cardamon and crystallized ginger. A friend of mine has a 5 year old nephew, who called her at 11 p.m. to tell her “I need some more of that black jelly cause it’s the best I ever had in my whole life”

A local Goodwill store is a great place to find an odd lid – I found an extra for my 3-quart Crock Pot (I bought the very first Crock Pot on the market back in the ’70s & it’s never been allowed to rest).

i made this yesterday. while it is indeed yummy, it did not firm up like a “butter”. how thick should it be getting in the slow cooker? i cooked it for at least another hour with the top off, stirring frequently to get the water to cook off. i ended up with 3 good-szd pint jars-full, but it was much more fluid than i would have thought.

does it have something to do with the age of the slowcooker? i see lots of posts about the older cookers. mine is newer, and large and oval-shaped. does that make a difference?

also, i would use less lemon zest. an entire lemon’s worth is a bit much, i think.

i would really appreciate some more info, as i liked this way of using all the blueberries on our bushes. i got all 8 cups from my own backyard.

Evi, every slow cooker is a little bit different and every batch is a bit different. The cooking time can vary a great deal depending on the amount of water in the fruit you’re using, the humidity in the air and the size and shape of your cooker. However, this is the beauty of making it yourself. You can cook it to your own specifications. If you want it to be thicker, you cook it longer. If you don’t like as much lemon zest, you simply use it less. You don’t have to follow my recipe to the T. I made it the way I like it. You should do the same.

thanks marissa – i’m not a super-inventive cook, especially with a process like canning and preserving, to which i am quite new. i like to try a recipe as it’s written first and then see if/how i might change it. just wanted some ideas on what the preferred viscosity would be at the end. should it be like whipped honey? like soft butter? like jam?

[…] a technique) via Food in Jars, which has taught me so much this year. This summer and fall, I made blueberry butter, peach apricot butter, and a Cortland apple butter that I freehanded one night when mom and dad […]

Can I use frozen berries? If so, would I need to let them thaw first or could I throw them in my Vitamix right from the freezer? I have been making yogurt in my slow cooker and I think this blueberry butter might just be the perfect topping, but it’s winter here in MN and the fresh blueberries are not much to be desired. Thanks!

I’ve not made this butter with frozen berries, so I can’t tell you how it will turn out. I will recommend that you let the berries at least partially thaw before you put them in the Vitamix, just so it’s a little easier on the machine.

I just made the blueberry butter (from the book) and I used frozen blueberries. I think that was a mistake because the yield was much smaller. At the end it only made less than 4 half-pint jars. I will cook down some more blueberries tomorrow and add it to the rest of the batch. That would explain though why the cinnamon and lemon taste is so strong.

I love the idea of blueberries and the slow cooker. However, preserving/canning has never been anything I was willing to try. Small NY apartment, space being one issue. Is this something I could freeze in small portions?

[…] used Marisa’s recipe for blueberry butter. It is featured in her book, as well as on her blog here. Instead of lemon zest, though, I used lemon verbena. I think it lended a nice earthy note to this […]

[…] has blogged about a wide variety of fruit butters she’s experimented with: check out her blueberry butter, apricot-peach butter, tomato butter, or her primer on slow-cooker fruit butters. They all look […]

Just finished canning this! The only adaptations I made were eyeballing a out a tablespoon of pumpkin pie spice instead of cinnamon and squeezed in the juice from the lemon! Yummy recipe! Will make it again next summer!

I just made this tonight. SO EASY and so yummy! Next time I’m going to experiment a little more, but this recipe is incredible as is. Thank you for helping me find a use for more of my blueberries – I bought 15lbs!

[…] used Marisa’s recipe for blueberry butter. It is featured in her book, as well as on her blog here. Instead of lemon zest, though, I used lemon verbena. I think it lended a nice earthy note to this […]

[…] onto warm pancakes slathered in butter. Mmmmm. The blueberry butter was done in a slow cooker via Food in Jars. She describes it as “blueberry pie in a jar” and I think it reminds me of Christmas. […]